xref: /libcore/luni/src/main/java/org/apache/harmony/xnet/provider/jsse/TrustManagerImpl.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.harmony.xnet.provider.jsse;

import java.security.InvalidAlgorithmParameterException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.cert.CertPath;
import java.security.cert.CertPathValidator;
import java.security.cert.CertPathValidatorException;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.PKIXParameters;
import java.security.cert.TrustAnchor;
import java.security.cert.X509Certificate;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import javax.net.ssl.X509TrustManager;

/**
 *
 * TrustManager implementation. The implementation is based on CertPathValidator
 * PKIX and CertificateFactory X509 implementations. This implementations should
 * be provided by some certification provider.
 *
 * @see javax.net.ssl.X509TrustManager
 */
public final class TrustManagerImpl implements X509TrustManager {

    /**
     * The AndroidCAStore if non-null, null otherwise.
     */
    private final KeyStore rootKeyStore;

    /**
     * The backing store for the AndroidCAStore if non-null. This will
     * be null when the rootKeyStore is null, implying we are not
     * using the AndroidCAStore.
     */
    private final TrustedCertificateStore trustedCertificateStore;

    private final CertPathValidator validator;

    /**
     * An index of TrustAnchor instances that we've seen. Unlike the
     * TrustedCertificateStore, this may contain intermediate CAs.
     */
    private final TrustedCertificateIndex trustedCertificateIndex;

    /**
     * This is lazily initialized in the AndroidCAStore case since it
     * forces us to bring all the CAs into memory. In the
     * non-AndroidCAStore, we initialize this as part of the
     * constructor.
     */
    private final X509Certificate[] acceptedIssuers;

    private final Exception err;
    private final CertificateFactory factory;

    /**
     * Creates X509TrustManager based on a keystore
     *
     * @param ks
     */
    public TrustManagerImpl(KeyStore keyStore) {
        CertPathValidator validatorLocal = null;
        CertificateFactory factoryLocal = null;
        KeyStore rootKeyStoreLocal = null;
        TrustedCertificateStore trustedCertificateStoreLocal = null;
        TrustedCertificateIndex trustedCertificateIndexLocal = null;
        X509Certificate[] acceptedIssuersLocal = null;
        Exception errLocal = null;
        try {
            validatorLocal = CertPathValidator.getInstance("PKIX");
            factoryLocal = CertificateFactory.getInstance("X509");

            // if we have an AndroidCAStore, we will lazily load CAs
            if ("AndroidCAStore".equals(keyStore.getType())) {
                rootKeyStoreLocal = keyStore;
                trustedCertificateStoreLocal = new TrustedCertificateStore();
                acceptedIssuersLocal = null;
                trustedCertificateIndexLocal = new TrustedCertificateIndex();
            } else {
                rootKeyStoreLocal = null;
                trustedCertificateStoreLocal = null;
                acceptedIssuersLocal = acceptedIssuers(keyStore);
                trustedCertificateIndexLocal
                        = new TrustedCertificateIndex(trustAnchors(acceptedIssuersLocal));
            }

        } catch (Exception e) {
            errLocal = e;
        }
        this.rootKeyStore = rootKeyStoreLocal;
        this.trustedCertificateStore = trustedCertificateStoreLocal;
        this.validator = validatorLocal;
        this.factory = factoryLocal;
        this.trustedCertificateIndex = trustedCertificateIndexLocal;
        this.acceptedIssuers = acceptedIssuersLocal;
        this.err = errLocal;
    }

    private static X509Certificate[] acceptedIssuers(KeyStore ks) {
        try {
            // Note that unlike the PKIXParameters code to create a Set of
            // TrustAnchors from a KeyStore, this version takes from both
            // TrustedCertificateEntry and PrivateKeyEntry, not just
            // TrustedCertificateEntry, which is why TrustManagerImpl
            // cannot just use an PKIXParameters(KeyStore)
            // constructor.

            // TODO remove duplicates if same cert is found in both a
            // PrivateKeyEntry and TrustedCertificateEntry
            List<X509Certificate> trusted = new ArrayList<X509Certificate>();
            for (Enumeration<String> en = ks.aliases(); en.hasMoreElements();) {
                final String alias = en.nextElement();
                final X509Certificate cert = (X509Certificate) ks.getCertificate(alias);
                if (cert != null) {
                    trusted.add(cert);
                }
            }
            return trusted.toArray(new X509Certificate[trusted.size()]);
        } catch (KeyStoreException e) {
            return new X509Certificate[0];
        }
    }

    private static Set<TrustAnchor> trustAnchors(X509Certificate[] certs) {
        Set<TrustAnchor> trustAnchors = new HashSet<TrustAnchor>(certs.length);
        for (X509Certificate cert : certs) {
            trustAnchors.add(new TrustAnchor(cert, null));
        }
        return trustAnchors;
    }

    @Override public void checkClientTrusted(X509Certificate[] chain, String authType)
            throws CertificateException {
        checkTrusted(chain, authType);
    }

    @Override public void checkServerTrusted(X509Certificate[] chain, String authType)
            throws CertificateException {
        checkTrusted(chain, authType);
    }

    private void checkTrusted(X509Certificate[] chain, String authType)
            throws CertificateException {
        if (chain == null || chain.length == 0 || authType == null || authType.length() == 0) {
            throw new IllegalArgumentException("null or zero-length parameter");
        }
        if (err != null) {
            throw new CertificateException(err);
        }

        Set<TrustAnchor> trustAnchors = new HashSet<TrustAnchor>();
        X509Certificate[] newChain = cleanupCertChainAndFindTrustAnchors(chain, trustAnchors);
        if (newChain.length == 0) {
            // chain was entirely trusted, skip the validator
            return;
        }

        CertPath certPath = factory.generateCertPath(Arrays.asList(newChain));
        if (trustAnchors.isEmpty()) {
            throw new CertificateException(new CertPathValidatorException(
                    "Trust anchor for certification path not found.", null, certPath, -1));
        }

        try {
            PKIXParameters params = new PKIXParameters(trustAnchors);
            params.setRevocationEnabled(false);
            validator.validate(certPath, params);
            // Add intermediate CAs to the index to tolerate sites
            // that assume that the browser will have cached these.
            // The server certificate is skipped by skipping the
            // zeroth element of new chain and note that the root CA
            // will have been removed in
            // cleanupCertChainAndFindTrustAnchors.  http://b/3404902
            for (int i = 1; i < newChain.length; i++) {
                trustedCertificateIndex.index(newChain[i]);
            }
        } catch (InvalidAlgorithmParameterException e) {
            throw new CertificateException(e);
        } catch (CertPathValidatorException e) {
            throw new CertificateException(e);
        }
    }

    /**
     * Clean up the certificate chain, returning a cleaned up chain,
     * which may be a new array instance if elements were removed.
     * Theoretically, we shouldn't have to do this, but various web
     * servers in practice are mis-configured to have out-of-order
     * certificates, expired self-issued root certificate, or CAs with
     * unsupported signature algorithms such as
     * md2WithRSAEncryption. This also handles removing old certs
     * after bridge CA certs.
     */
    private X509Certificate[] cleanupCertChainAndFindTrustAnchors(X509Certificate[] chain,
                                                                  Set<TrustAnchor> trustAnchors) {
        X509Certificate[] original = chain;

        // 1. Clean the received certificates chain.
        int currIndex;
        // Start with the first certificate in the chain, assuming it
        // is the leaf certificate (server or client cert).
        for (currIndex = 0; currIndex < chain.length; currIndex++) {
            // If the current cert is a TrustAnchor, we can ignore the rest of the chain.
            // This avoids including "bridge" CA certs that added for legacy compatability.
            TrustAnchor trustAnchor = findTrustAnchorBySubjectAndPublicKey(chain[currIndex]);
            if (trustAnchor != null) {
                trustAnchors.add(trustAnchor);
                currIndex--;
                break;
            }
            // Walk the rest of the chain to find a "subject" matching
            // the "issuer" of the current certificate. In a properly
            // order chain this should be the next cert and be fast.
            // If not, we reorder things to be as the validator will
            // expect.
            boolean foundNext = false;
            for (int nextIndex = currIndex + 1; nextIndex < chain.length; nextIndex++) {
                if (chain[currIndex].getIssuerDN().equals(chain[nextIndex].getSubjectDN())) {
                    foundNext = true;
                    // Exchange certificates so that 0 through currIndex + 1 are in proper order
                    if (nextIndex != currIndex + 1) {
                        // don't mutuate original chain, which may be directly from an SSLSession
                        if (chain == original) {
                            chain = original.clone();
                        }
                        X509Certificate tempCertificate = chain[nextIndex];
                        chain[nextIndex] = chain[currIndex + 1];
                        chain[currIndex + 1] = tempCertificate;
                    }
                    break;
                }
            }
            // If we can't find the next in the chain, just give up
            // and use what we found so far. This drops unrelated
            // certificates that have nothing to do with the cert
            // chain.
            if (!foundNext) {
                break;
            }
        }

        // 2. If the chain is now shorter, copy to an appropriately sized array.
        int chainLength = currIndex + 1;
        X509Certificate[] newChain = ((chainLength == chain.length)
                                      ? chain
                                      : Arrays.copyOf(chain, chainLength));

        // 3. If no TrustAnchor was found in cleanup, look for one now
        if (trustAnchors.isEmpty()) {
            TrustAnchor trustAnchor = findTrustAnchorByIssuerAndSignature(newChain[chainLength-1]);
            if (trustAnchor != null) {
                trustAnchors.add(trustAnchor);
            }
        }
        return newChain;
    }

    /**
     * Check the trustedCertificateIndex for the cert to see if it is
     * already trusted and failing that check the KeyStore if it is
     * available.
     */
    private TrustAnchor findTrustAnchorBySubjectAndPublicKey(X509Certificate cert) {
        TrustAnchor trustAnchor = trustedCertificateIndex.findBySubjectAndPublicKey(cert);
        if (trustAnchor != null) {
            return trustAnchor;
        }
        if (trustedCertificateStore == null) {
            // not trusted and no TrustedCertificateStore to check
            return null;
        }
        // probe KeyStore for a cert. AndroidCAStore stores its
        // contents hashed by cert subject on the filesystem to make
        // this faster than scanning all key store entries.
        if (trustedCertificateStore.isTrustAnchor(cert)) {
            // add new TrustAnchor to params index to avoid
            // checking filesystem next time around.
            return trustedCertificateIndex.index(cert);
        }
        return null;
    }

    private TrustAnchor findTrustAnchorByIssuerAndSignature(X509Certificate lastCert) {
        TrustAnchor trustAnchor = trustedCertificateIndex.findByIssuerAndSignature(lastCert);
        if (trustAnchor != null) {
            return trustAnchor;
        }
        if (trustedCertificateStore == null) {
            return null;
        }
        // we have a KeyStore and the issuer of the last cert in
        // the chain seems to be missing from the
        // TrustedCertificateIndex, check the KeyStore for a hit
        X509Certificate issuer = trustedCertificateStore.findIssuer(lastCert);
        if (issuer != null) {
            return trustedCertificateIndex.index(issuer);
        }
        return null;
    }

    @Override public X509Certificate[] getAcceptedIssuers() {
        return (acceptedIssuers != null) ? acceptedIssuers.clone() : acceptedIssuers(rootKeyStore);
    }
}